Oral squamous-cell carcinoma (OSCC) is classified as a head and neck carcinoma and is a tumor that is mainly generated from oral mucous membrane epithelia and the like. Among head and neck carcinomas, OSCC incidence is as high as about 35% and it is assumed to develop in about 270,000 people worldwide every year (Parkin, D. M., et al., CA Cancer J Clin. 55, 74-108, 2002). In Japan, 5,500 or more people had died thereof in 2003. The most common site of the origin of oral squamous-cell carcinoma is tongue and the second most common site thereof is gingiva (gum). Oral squamous-cell carcinoma is known to be developed at other mucous membranes of the oral cavity such as buccal mucosa, palate, and mouth floor. Furthermore, oral squamous-cell carcinoma is also known to be developed at jawbone or salivary gland.
In recent years, although methods for diagnosis and treatment for oral squamous-cell carcinoma have been advanced, the prognosis thereof has remained unimproved. Accordingly, it has been necessary to discover a causative gene for oral squamous-cell carcinoma and changes that have occurred in such gene to elucidate the functions for establishment of new therapeutic strategy for development of more effective therapeutic methods and chemical prevention.